SixDegrees.com was a social network service website that lasted from 1997 to 2001 and was based on the Web of Contacts model of social networking. It was named after the six degrees of separation concept and allowed users to list friends, family members and acquaintances both on the site and externally; external contacts were invited to join the site. Users could send messages and post bulletin board items to people in their first, second, and third degrees, and see their connection to any other user on the site. It was one of the first manifestations of social networking websites in the format now seen today. Six Degrees was followed by more successful social networking sites based on the "social-circles network model" such as Friendster, MySpace, LinkedIn, XING, and Facebook.